The late-night host is throwing an "epic two-night concert event" (as his people put it in a press release) with free outdoor gigs by the two boy-band veterans, both on Hollywood Boulevard between Highland Avenue and Sycamore Avenue.

On Monday night, ex-Beatle McCartney will take the stage ahead of the release next month of "New," his first set of original songs since since 2007.

Then, on Tuesday, former (and perhaps future?) 'N Sync member Timberlake will perform material from "The 20/20 Experience -- 2 of 2," the new album he's putting out Sept. 30. (Tickets are available -- or at least they were -- at JKLTickets.)

Both men, by the way, will hit L.A. fresh from this weekend's iHeartRadio Music Festival in Las Vegas, where they're to appear alongside Katy Perry, Bruno Mars, Drake, Elton John and Miley Cyrus, among many others.

Stay tuned to Pop & Hiss for coverage of that blow-out beginning Friday, and watch the lyric video for McCartney's single "New" below.